The present invention disclosed herein relates to a technology for providing a supply voltage to a power amplifier and, more particularly, to a method of generating a driving signal for driving a dual mode supply modulator for a power amplifier in a transmission structure of a 3-level envelope delta-sigma modulator (EDSM).
Modern communication standards such as IEEE 802.16 and 3rd generation partnership project (3GPP) long term evolution (LTE) use a complex modulation scheme for obtaining a high data rate in limited frequency resources. Due to this, a transmission signal has a high peak-to-average power ratio (PAPR), which results in an unfavorable condition in efficiency performance
Since current base station system aims miniaturization, a higher efficient power amplifier structure is necessary than any other time.
An envelope elimination and restoration (EER) transmission structure is one of high efficiency power amplifier structures and has a structure of separating envelope and phase components, processing them respectively, and recombining them.
Typically, an EER structure means a Kahn structure, but all structures for separating envelope and phase components of a signal and processing them, such as an improved Kahn structure or a digital polar modulator (DPM) structure, may be called as the EER structure.
Among the EER structure, a structure for applying a delta-sigma modulator (DSM) to an envelope component is particularly called as an envelope delta-sigma modulator (EDSM) structure.
In a three-level EDSM transmission structure, when a power amplifier is configured with a single transistor, dual supply voltages are necessary for the high efficient operation of the power amplifier.
For this, a dual mode supply modulator which provides dual supply voltages according to a driving signal is used, and the function thereof is to provide dual supply voltages (‘VDD low’ and ‘VDD high’) according to a driving signal of two levels (VL, VH). That is, when the driving signal is VL, the dual mode supply modulator provides VDD low, and when the driving signal is VH, it provides VDD high. Accordingly, in order to provide the dual supply voltages to the power amplifier properly, it is necessary to form the signal for driving the dual mode supply modulator properly.